EFFECTS OF NITRATE/AMMONIUM RATIO, NITROGEN SOURCE, TEMPERATURE, RELATIVE HUMIDITY, AND LIGHT INTENSITY ON GROWTH AND CALCIUM UPTAKE, TRANSLOCATION, AND ACCUMULATION IN SORGHUM (SORGHUM BICOLOR (L.) MOENCH)

Information about calcium utilization in sorghum is limited. Five sets of experiments were conducted to study the effects of (1) different NO(,3)(\u27-)/NH(,4)+ ratios and N sources, (2) different temperature and relative humidity regimes, and (3) different light intensity regimes in combinations with different Ca levels on plant growth and the uptake, translocation, and accumulation of Ca in sorghum. Parameters used to measure the effects of treatments on \u27Redlan\u27 and \u27Martin\u27 plants were Ca deficiency symptoms, Ca uptake and distribution, Ca distribution within leaves, dry matter yields, total dry matter produced per total Ca absorbed (CaE1) or per Ca concentration (CaU1) or per total N absorbed (NE1), N/Ca ratios, shoot/root dry matter ratios, solution pH, and plant concentrations of Mg, P, S, Cl, Mn, Fe, Cu, and Zn. Plants grown in solution with a higher proportion of NH(,4)+ than NO(,3)(\u27-), high temperature regime, or 60% relative humidity in combination with low solution Ca developed Ca deficiency symptoms. Calcium deficiency symptoms were characterized by young leaves curling and the edges becoming serrated. Marginal necrosis appeared only at the later and more severe states of deficiency. Solution pH increased with increasing NO(,3)(\u27-) supply. Calcium concentrations in the plant parts increased as the amount of NO(,3)(\u27-) or Ca(\u272+) in the solutions increased. Dry matter yields increased as NO(,3)(\u27-)/NH(,4)+ ratios increased and was more pronounced with higher Ca in solution. Plants grown in Ca(NO(,3))(,2) solutions generally had the highest Ca concentrations and dry matter yields followed by plants grown with urea, NH(,4)NO(,3), and (NH(,4))(,2)SO(,4), respectively. Nondeficient plants had low N/Ca, CaE1, and CaU1 values. Higher NE1 values were also associated with nondeficient plants. Lower leaves had higher Ca concentrations than upper leaves reflecting Ca immobility. Calcium concentrations in each leaf increased from the base to the tip. Plants grown under a relatively lower temperature regime produced more dry matter. Highest dry matter yields were produced in plants grown at 30% relative humidity, and the minimum yields when grown at 60% humidity. Dry matter yields, number of tillers, and shoot/root values increased with increased light intensity